1. Field of the Invention
The present invention relates to an improvement in a one-way clutch used in a transmission, particularly an automatic transmission of a motor vehicle, an agricultural machine, a construction machine, an industrial machine and the like. More particularly, the present invention relates to a one-way clutch having a lock-up function.
2. Related Background Art
A conventional one-way clutch used in an automatic transmission has an outer race and an inner race which are rotated relative to each other, and sprags or rollers for transmitting torque between the outer race and the inner race are engaged by a cam surface provided on a track surface of the outer race or the inner race, thereby transmitting rotational torque only in one direction. Further, such a one-way clutch is idly rotated in reverse direction.
Such a one-way clutch cannot be used in case that rotation must be transmitted in both of two directions. In such cases, by combining the one-way clutch with a multi plate clutch such as a multi-plate frictional engaging device for effecting lock-up, a clutch is designed so that a rotary member is idly rotated only in one direction or the rotary member is prevented from being idly rotated in both of two directions, on demand.
However, in such an arrangement, the function for effecting idle rotation only in one direction and the function for preventing idle rotation in both directions must be shared with two members, with the result that there arise problems such as an increase in the number of parts, complexity, bulkiness, an increase in weight and an increase in cost.